1. Field of the Invention
The disclosures herein generally relate to a projection optical apparatus and an image projection apparatus.
2. Description of the Related Art
There have been widely used projectors configured to project image data transmitted from PCs or video cameras onto screens or the like. In such projectors, various types of malfunctions may be observed due to heat generated by light sources or heat transferred by the light sources onto parts of the projectors, which may degrade the quality of the displayed images.
To control such malfunctions, there are proposed thermal countermeasure structures for the projectors (e.g., Japanese Laid-open Patent Publication No. 2008-51919 hereinafter referred to as “Patent Document 1”). The thermal countermeasure structures partition the inside of a projector between a heat generating section that contains a light source and a heat control section that contains a circuit board and the like. In the thermal countermeasure structure, heat transferred from the heat generating section is cut off by a mediator to control the temperature of the circuit board and the like from rising in the heat control section.
However, in such a thermal countermeasure structure, an optical system such as lenses disposed together with the light source in the heat generating section may still be susceptible to the temperature rise by receiving heat from a light source or infrared components of the light emitted from the light source. For example, when lenses or lens holders holding the lenses are heated to raise the temperatures to thermally expand, projection directions or focal positions may fluctuate due to the displacement of the lens positions and the like, which may degrade the quality of the display images.